EFFECTS OF ALPHA–NAPHTHALENEACETIC ACID AND ALPHA–NAPHTHALENEACETAMIDE ON THE DEVELOPMENT OF THE COTTON PLANT

Abstract

DESPITE THE extensive literature on effects of growth substances on development of plants, there are very few reports on influences of growth substances on cotton plant. While there have been a number of attempts to reduce boll abscission by use of growth substances, these have not been successful and few of them have been reported in literature. Dunlap (1945) reported negative results when he used several growth substances including naphthaleneacetic acid, and Eaton and Rigler (1945) stated that the present information does not permit any well-defined application of observation or theory to relations between hormone activity and shedding of cotton bolls, but some of marked differences between cottons in extent to which shedding occurs would seem to preclude possibility that in all cases this shedding can be attributed solely to nutritional relations. Except for limited amount of work on growth substances in relation to boll shedding, there has apparently been no work done on influences of growth substances on cotton. Any adequate review of influence of growth substances on plant development in general would be unwieldy and unnecessary here, so further citations of literature will be restricted to papers pertinent to discussion which appears later in this paper. The present study was initiated primarily to investigate possible influence of growth substances on boll abscission, but other effects were also observed and measured. As experiment progressed it became apparent that a general study of effects of growth substances would be more valuable than a specific studv of abscission, especially since so little has been reported on effects of growth substances on development of cotton plant. The results show that a-naphthaleneacetic acid, and to a lesser degree a-naphthaleneacetamide, have definite effects on growth and development of cotton plant. In general, growth was inhibited rather than stimulated by treatments, and it is unlikely that any of effects are of interest from standpoint of agronomic application, either as regards boll abscission or otherwise. 1 Received for publication April 23, 1949. This paper is a complete revision and condensation by junior author of a thesis submitted by senior author (1948) in partial fulfillment of requirements for degree of master of science at A. and M. College of Texas. The authors wish to acknowledge with thanks suggestions made by Dr. A. A. Dunlap, checking of statistical analyses by Prof. C. B. Godbey, critical reading of this manuscript by Dr. Frank M. Eaton, and testing of cotton fibers by Mr. J. L. Watson. METHODS.-Several seeds of Stoneville 2B variety of cotton (Gossypium hirsutum L.) were planted in each of a number of 2-gal. glazed jars on February 28, 1948, and by March 6 plants had been thinned to one per jar. The plants were maintained in fertile soil under good greenhouse cultural conditions throughout experiment, and